The present invention broadly relates to self-propelled or self-steering or driverless floor vehicles and pertains, more specifically to a new and improved method of guiding a self-steering vehicle along an optical guideway. The present invention also relates to a new and improved apparatus for guiding a self-steering vehicle according to the inventive method.
Driverless floor transport vehicles are known, for example, from a reprint of a paper entitled "Fahrerlose Flurforderzeuge--Hilfen auf dem Wege zur Automatisierung" (translated as "Driverless floor transport vehicles--resources on the way to automation") by P. Gunsser in TEXTIL PRAXIS INTERNATIONAL 1984, volume 7, pages 661 through 664, such vehicles being electromagnetically guided or steered along a guide cable or wire by means of sensors mounted at the vehicle, such guide cable or wire being laid in the floor. This implies that a groove for laying the guide cable or wire has to be cut or milled into the floor, particularly in the case of subsequent installation of such a vehicle guide system. This is relatively costly and, with certain floor materials, would require an extensive preparatory operation not readily carried out.
Furthermore, systems are known in which, instead of a guide cable or wire, there is provided on the floor an optical strip which is scanned by means of sensors, such sensors emitting or radiating a pulsed light beam.
In such systems there are generally used two sensors which are mounted at the vehicle in such a manner that the spacing or distance between the two sensors, as viewed transversely relative to the direction of travel, is slightly larger than the width of the optical strip. In other words, the sensors signal whether the light beam is reflected from the guide strip or from the floor close to the guide strip and, in the event of a corresponding deviation, trigger a control signal for a steering or guiding mechanism. Since this prior art system is only constructed for two conditions, namely "light" and "dark", the system operates in a too coarse and too inaccurate manner, particularly since damage to the guide strip and dirt on the floor are detected by the two sensors as an incorrect or erroneous signal and result in a faulty guide or steering signal.
Control systems are also known, for example, from a paper entitled "Neue Systeme zur Steuerung von Flurforderzeugen" (translated as "New systems for controlling floor transport vehicles") by Hartmut Jorichs in TECHNISCHE RUNDSCHAU, volume 1/89, pages 34 through 39, in which the guidance of a vehicle is effected by means of lasers or by scanning the walls by means of ultrasonic waves. In such control systems, the path or guideway for the vehicle cannot be appraised by the human eye. Accordingly, these systems are only suitable for areas without any operating personnel.
The guidance by means of pattern recognition or identification and picture analysis or interpretation by a camera would require a corresponding constructional expenditure and, therefore, represents a costly system which would be susceptible to disturbances.